Fungi are known to cause a variety of infectious diseases in man, animals, and plants. In man, for instance, they cause superficial mycosis affecting the skin, oral cavity, etc. and systemic mycosis affecting the viscera, brain, etc. They cause similar infections in pet and domestic animals as well. Furthermore, fungi inflict various hazardous effects on plants such as orchard trees and vegetables.
As the principal pathogenic fungi causing systemic mycosis in man, those of the genera Candida, Cryptococcus, and Aspergillus, among others, are known. As to superficial mycosis, Candida species affecting the skin, oral cavity, and vagina and trichophytons infecting the skin of the extremities are regarded as the major pathogenic fungi. Besides those fungi, many other fungi exist in the environment and are suspected to contaminate the animal and vegetable kingdoms.
As antimycotics of use for the prevention and treatment of such fungal infections and contaminations, only a very few are known. As therapeutic drugs for systemic mycosis in man and animals, for instance, amphotericin B, flucytosine, miconazole, and fluconazole can be mentioned. However, those compounds are not fully satisfactory in potency, toxic potential, or antifungal spectrum, thus being not impeccable as therapeutic drugs.
In view of the above-mentioned prior art, the present invention has for its object to provide a novel antibiotic which is of value as a therapeutic agent for fungal infections.
In the search for a novel antibiotic, the inventors of the present invention isolated a large number of microorganisms from the natural kingdom, isolated the antibiotics they produced, and scrutinized their biological properties. As a result, they discovered that the culture broth of a strain of microorganism of the Fungi Imperfecti contained an antibiotic having antifungal activity against pathogenic fungi inclusive of Candida albicans, C. kefyr, Cryptococcus neoformans, and Aspergillus fumigatus. Accordingly the inventors isolated this antibiotic and studied its physicochemical properties. As a result, they discovered that it was a novel substance having distinct physicochemical characteristics, which had been described in no literatures yet, and named it TKR2999. The present invention intends to provide the above antibiotic TKR2999 and a method of production thereof.
The present inventions are described in detail as follows.